| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 |
0.5%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 349 |
47.9%
|
| 1 | Minor obstacle | 154 |
21.1%
|
| 2 | Moderate obstacle | 111 |
15.2%
|
| 3 | Major obstacle | 49 |
6.7%
|
| 4 | Very severe obstacle | 61 |
8.4%
|